1. Field of the Invention
This invention relates to a method of manufacturing a porous elastic membrane, and in particular a porous membrane that can be used to form the walls of a balloon assembly of a balloon catheter.
2. Description of Related Art
During a medical procedure known as percutaneous transluminal coronary angioplasty (xe2x80x9cPTCAxe2x80x9d), a balloon catheter is inserted into an artery. A balloon assembly of the balloon catheter is then inflated to compress an atherosclerosis and dilate the walls of the artery. A therapeutic agent is then administered to the inner walls of the artery through small apertures in the outside wall of the balloon assembly. The balloon catheter""s capability to locally administer a therapeutic agent to the dilated portion of the artery can be effective in limiting restenosis.
Porous, elastic balloons and methods of making such balloons are disclosed in U.S. Pat. No. 5,318,531 to Leone; U.S. Pat. No. 5,049,132 to Shaffer et al.; U.S. Pat. No. 5,860,954 to Ropiak; and U.S. Pat. No. 5,254,089 to Wang. The apertures through the balloon may be formed by mechanical punching, mechanical drilling, directing a laser beam at the elastic material, directing an ion beam at the elastic material, or directing an electron beam at the elastic material, among other possibilities. Typically, the cost of making the apertures is inversely proportional to their diameters.
Apertures formed by mechanical drilling or poking are not always of the precise shape and size desired, or may have tiny flaws which could affect the smooth delivery of therapeutic agents. Moreover, the size of the aperture is limited by the ability to make ever finer tools. Apertures formed using a laser, an ion beam, or an electron beam, while potentially having smaller and more regular diameters, are time consuming and expensive to make. Accordingly, there is a need for an inexpensive method of precisely forming tiny apertures in an elastic membrane for use in a balloon catheter.
The present invention provides methods for forming a porous membrane, which may be used, for example, to form the outside wall of a balloon assembly of a balloon catheter.
One embodiment of the present invention includes expanding an elastic material beyond an intended deployment expansion to a hyper-expanded expansion. A plurality of apertures are formed through the hyper-expanded elastic material. The diameter of the apertures as formed is larger than the diameter of the apertures at the intended deployment expansion.
In accordance with another embodiment of the present invention, a method for forming a porous balloon is provided. The method includes forming a balloon of an elastic material. The balloon has an outer wall with an intended deployment diameter D1. The balloon is inflated to a diameter D2, wherein D2 is greater than D1. A plurality of apertures are formed in the outer wall. The apertures so formed have a diameter d2. The balloon is then deflated for insertion into a patient""s body. In the patient""s body, the balloon is inflated to the intended deployment diameter D1, at which point the apertures have an intended deployment diameter of d1. Diameter d1 is less than the diameter d2 of the apertures when the apertures were formed.
Since the cost and time required to make a porous membrane for a balloon catheter or some other device is a function of the aperture size, with smaller holes being more costly and time consuming to make, the present invention provides for significant savings.